Re: [PATCH v3 bpf-next 14/18] bpf: Compare BTF types of functions arguments with actual types

From: Song Liu <songliubraving@fb.com>
To: Alexei Starovoitov <ast@kernel.org>
Cc: David Miller <davem@davemloft.net>,
	"daniel@iogearbox.net" <daniel@iogearbox.net>,
	"x86@kernel.org" <x86@kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v3 bpf-next 14/18] bpf: Compare BTF types of functions arguments with actual types
Date: Fri, 8 Nov 2019 17:32:34 +0000	[thread overview]
Message-ID: <0E317F4C-F81F-43D2-9B8E-D8EE93C98A07@fb.com> (raw)
In-Reply-To: <0A1C27F0-25D9-455C-86DF-97AC19674D8D@fb.com>

> On Nov 8, 2019, at 9:28 AM, Song Liu <songliubraving@fb.com> wrote:
> 
> 
> 
>> On Nov 7, 2019, at 10:40 PM, Alexei Starovoitov <ast@kernel.org> wrote:
>> 
>> Make the verifier check that BTF types of function arguments match actual types
>> passed into top-level BPF program and into BPF-to-BPF calls. If types match
>> such BPF programs and sub-programs will have full support of BPF trampoline. If
>> types mismatch the trampoline has to be conservative. It has to save/restore
>> all 5 program arguments and assume 64-bit scalars. If FENTRY/FEXIT program is
>> attached to this program in the future such FENTRY/FEXIT program will be able
>> to follow pointers only via bpf_probe_read_kernel().
>> 
>> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> 
> Acked-by: Song Liu <songliubraving@fb.com>

One nit though: maybe use "reliable" instead of "unreliable"

+struct bpf_func_info_aux {
+	bool reliable;
+};
+

+	bool func_proto_reliable;

So the default value 0, is not reliable. 

Thanks,
Song